A good question that I assume is the point of the Defense asking for the disclosures. Seems like Libby has hired good defense attorney's and it seems that Fitzgerald is going to look like a bumbling idiot by the time this is over.
The point is, under the perjury and false statements statutes, a lie must be about a material fact in the investigation. If, as here, there was no underlying crime and the prosecution knew or should have known it, then a lie would not be material and the case should be dismissed.